418 



TEOCHTNiE. 



There is usually a single, strong tooth at the fore part 

 of the columella in this genus, and the operculum is 

 orbicular and many-whorled. 



Species of Monodonta. 



australis, La77i. 

 canalifera, Lam. 

 circumcincta, A. Adams. 

 dama, Phil. 

 exigua, A. Adams. 

 labio, Li7in. 

 neritoides, Phil. 



parva, Trosch. 

 rugulosa, A. Adams. 

 spilota, A. Adorns. 

 tuberculata, A. Adams. 

 turbiuata, Gmel. 

 viridis, Lam. 



Genus EUCHELUS, Philippi. 



Operculum ovate, of iew, rapidly-enlarging whorls. 



Shell turbinately conoidal, whorls rounded, with trans- 

 verse, granular ribs, axis usually perforated ; columella 

 acute, with a small tooth at the fore part ; aperture cir- 

 cular ; outer lip thick, obtuse, rounded, internally crenate. 



Syn. Euchele, Pliil. Aradasia, Gray. 



Ex. E. denigratus, Chemnitz, pi. 47, fig. 6. Oper- 

 culum, E. denigratus, fig. 6, a. Shell, E. denigratus, fig. 

 6, h. 



The sheJls of this genus are usually umbilicated, and 

 the whorls are always adorned with transverse, granular 

 ribs ; there is a single tooth on the columella, and the 

 operculum is ovate, and of comparatively few whorls. 



Species of Euchelus. 



alveolatus, A. Adams. 

 asper, Chem. 



baccatus, Mke. 

 circulatus, Anton. 



